This invention relates to the use of a combined expansion valve with a downstream restrictions on separate flow lines leading into a single evaporator. The combination provides better control over the refrigerant flow.
Refrigerant cycles as commonly utilized incorporate an evaporator coil which receives a refrigerant through a plurality of tubes. Typically, the flow of refrigerant will vary across the evaporator coil, and thus the evaporator efficiency is not usually at optimum levels. It would be desirable to provide a system wherein the flow of refrigerant across various positions within the evaporator could be better controlled.
Systems have been suggested wherein there are a plurality of separate refrigerant flow lines each having an expansion valve leading into the evaporator. By varying the several expansion valves, control over the refrigerant in the various positions in the evaporator coil can be achieved. However, this is very complex and expensive. The restrictions can be as simple as a narrowing in the flow line. Further, it is expected and preferred that across the evaporator, restrictions will vary in diameter, and other design characteristics.
Other known systems have utilized a distributor receiving fluid flow from the main expansion valve. The refrigerant leaving the main expansion valve has typically changed into being two-phase, with a mixture of approximately 75% liquid and 25% vapor refrigerant. Of course, the proportions may vary. For the evaporator coil to operate efficiently, each circuit path should receive about the same mixture of liquid and vapor. The distributor""s purpose is to insure the flow leading to each of the separate inlets in the coil is roughly the same amount of liquid and vapor. However, such an arrangement requires lengthy tubing, and resulting high cost and labor intensive assembly.
In the disclosed embodiment of this invention, a main expansion valve is positioned in series with an inlet header having a series of restrictions leading into an evaporator coil. The restrictions each communicate with one flow passage through the evaporator coil. Refrigerant leaving the condenser passes into the main expansion valve, and is expanded. The entire expansion work is not performed at the main expansion valve. Instead, from the expansion valve the refrigerant flows into an inlet header. The inlet header communicates with several flow passages each having individual restrictions. The flow passages communicate with separate flow lines through the evaporator coil. The separate restrictions allow individual control over each of the flow lines such that the refrigerant flow through various locations in the evaporator coil can be optimized. However, since the main expansion valve does the bulk of the expansion work, the restrictions can be relatively simple and inexpensive.
The use of the orifices allows specific control over each of the flow lines. Thus, the present invention provides a system which is able to better control the efficiency of refrigerant cycles with a relatively low cost solution.
Further, the use of the separate orifices on each line eliminates any need for a distributor. The orifices can be designed to insure a roughly equal mixture of liquid and vapor.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.